54 ALFEED GIBBS BOURNE. 



recorded by Beddard (1), but then in none of my specimens 

 was the clitellum very well developed.^ 



Clitellum. — The clitellum is not shown in my coloured 

 figure, as I was unable to secure a live worm in which it was 

 developed, but I have seen it in spirit specimens collected at 

 some other time of year. 



I have seen it developed upon the posterior portion of seg- 

 ment XIII, and upon every succeeding segment down to and in- 

 cluding segment xxi ; it is, however, always deficient ventrally 

 from segment xvii onwards, so that the male pores do not 

 actually open through clitellar substance.^ 



Genital Apertures. — The spermathecal apertures are 

 placed between segments vii . viii and viii . ix, or rather just 

 on the anterior margins (which is the usual arrangement) of the 

 hinder of those segments in each case. They are all placed 

 equally near the median ventral line, and about in a line with 

 seta 9 (i.e. the ninth seta from the median ventral line). 



The two oviducal apertures are placed very close together, and 

 very slightly in front of the seta ring in segment xiv^ (fig. 2). 



1 With regard to the presence or absence of setae on the clitellum a good 

 deal of unnecessary confusion exists. In all young pericbsete worms which I 

 have examined setse are present on the clitellar segments, but when the 

 clitellum develops they may remain projecting, or they may become buried 

 in the clitellar substance, or any or all of them may actually drop out. I am 

 inclined to think that all the species of one genus behave in the same way in 

 this respect, but am not sure of this. 



' I know of no perichsete worm in which the male pores do thus open. We 

 shall have to distinguish between worms in which the clitellum forms a definite 

 girdle, strictly limited in normal individuals to certain segments, and those in 

 which it always shows a tendency to spread somewhat irregularly. Even if 

 we abandon, as Vejdovsky (15) and Eosa (11, a) do, and as we certainly must, 

 Perrier's classification (8) of earthworms into Anteclitellians, Intraclitellians, 

 and Postclitellians, we may still use the character of the clitellum in classifi- 

 cation. 



^ I know of no Perichsete in which there are any setse between the oviducal 

 pores ; the latter always lie either in the ventral seta gap or slightly in front 

 of the seta ring altogether. It is often a very difiicult matter to ascertain 

 whether the oviducal pores are paired or single and median. 



I am now convinced that P. saletensis and P. bivagiuata, which I 



